I’m not sure any one series has a particularly great calendar. Each championship has it highlights…
Moto GP: Laguna Seca, Phillip Island, Mugello, Assen etc
IndyCar: Indianapolis, Watkins Glen, Long Beach
GT1: Portimao, San Luis, Paul Ricard
F1: Spa, Monaco, Suzuka, Melbourne, Interlagos etc
NASCAR: Road America, Montreal, Daytona
Add them all together and you get quite a calendar!